This invention relates to an error correcting typewriter and more particularly to an error correcting typewriter providing means for selectively effecting character-for-character correction or sequential letter or word obliteration and correction.
The prior art discloses typewriters embodying structures which require different sequences of operation for performing a correcting function. The prior art relating to error correcting typewriters is exemplified by the following U.S. Patents, Davidge et al., U.S. Pat. No. 3,799,316; Skrizipek, U.S. Pat. No. 4,108,557 and Gall et al., U.S. Pat. No. 4,203,681, each of which is directed to the correction of a single character in which the erroneous character is obliterated and a correct character is retyped in its place. However, if it is desired to obliterate a series of characters, as in a word or in a line, multiple operations must be repeated in order to effect such obliteration and correction. From a human engineering standpoint this is highly undesirable. Advantageously, the operator should be able to correct a word or line with a minimum number of typing strokes and without intensive concentration as to the sequence of steps required.
In Davidge et al., Pat. No. 3,799,316, which employs a letter-on-letter correction system the following sequence of operations is required for correcting a single letter:
(1) Position the carriage to the space immediately following the erroneous character. PA1 (2) Actuate a control key which causes the carriage to backspace a single space, conditions a correction medium (ribbon) to be operative for the next single print cycle, and disengages the carrier space escapement such that it remains inoperative only for the one following print cycle. PA1 (3) Actuate the erroneous letter printing key which effects a print function through the correction medium, resets the correction medium to the inoperative mode, and reengages the carrier escapement mechanism to its normal typing mode. PA1 (4) Actuate the correct character printing key. PA1 (1) Position the carriage to the space following the last letter of the word. PA1 (2) Actuate the control key to condition the machine and reverse space. PA1 (3) Actuate the print key corresponding to the character to be obliterated (subsequent operations repeat operations 2, then 3, then 2 until the entire word is obliterated). PA1 (1) Position the carriage to the space immediately following the erroneous character. PA1 (2) Actuate a control key which initiates a reverse space operation and subsequently conditions the correction medium to be operative, prints an obliterating area through the correction medium (ribbon) and returns the ribbon to the inoperative mode. No space escapement occurs due to the intentional failure to operate this mechanism. PA1 (3) Actuate the correct character printing key. PA1 (1) Position the carriage to the space following the last character of the word. PA1 (2) Actuate the control key to reverse space and obliterate the character (subsequent operations repeat operation 2 as required). PA1 (1) Position the carriage in line with the erroneous character. PA1 (2) Actuate a control key which conditions the correction medium to be operative, temporarily disables the carrier space escapement mechanism, prints the obliterating area through the correction medium, returns the correction medium to an inoperative mode and returns the character escapement mechanism to its normal typing mode. PA1 (3) Actuate the correct character printing key. PA1 (1) Position the carriage in line with the last or first character of the word. PA1 (2) Actuate the control key to obliterate the character. PA1 (3) Actuate the reverse space key or forward space bar.
If it is desired to obliterate a series of characters, such as a word or a line, the following sequence of operations is required:
In Skrizipek U.S. Pat. No. 4,108,557, which utilizes an obliterating blank type face, the following sequence of operations is required for the correction of a single character:
In order to obliterate a series of characters the following sequence of operations is required:
In Gall et al., U.S. Pat. No. 4,203,681 which utilizes an obliterating blank type face, the following sequence of operations is required for correcting a single character:
In order to obliterate a series of characters, the following sequence of operations is required:
In susequent operations repeat operation 2 then 3 then 2 and so forth, as required.